The potential difference that much be applied to stop the fastest photo electron emitted by a nickel surface having work function $5.01\;ev$ When ultra violet light 0f 200 nm falls on it , must be

Question

$\begin{array}{1 1} 2.4 \;V \\ -1.2\;V \\ -2.4 \;V \\ 1.2 \;V \end{array} $